This invention relates to methods for producing copper(I)-diamine complexes in solution and methods for producing polyphenylene oxides by the oxidative coupling of phenols utilizing copper(I)-diamine complexes formed in the polymerization medium to effect the reaction.
Polyphenylene oxides, sometimes known as polyphenylene ethers, are well known polymers useful as industrial resins. These polymers, both homopolymers and copolymers and processes for producing them are disclosed in U.S. Pat. Nos. 3,306,874; 3,306,875; 3,733,299 and 4,028,341, which are hereby incorporated herein by reference.
These polymers are typically prepared by the oxidative coupling of phenols in the presence of copper-halide-amine complex catalysts. Phenols which can be oxidatively coupled to provide polymers have the structural formula: ##STR1## where x is hydrogen, chlorine, bromine or iodine; Q is hydrogen, hydrocarbon radicals, halohydrocarbon radicals having at least two carbon atoms between the halogen atom and phenol nucleus, hydrocarbonoxy radicals and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen atom and the phenol nucleus; and Q' and Q" are selected from the same group as Q, and in addition, halogen, provided that Q, Q' and Q" are all free of a tertiary .alpha.-carbon atom.
A number of copper-halide amine catalyst systems have been disclosed. These are typically prepared prior to polymerization by blending cuprous or cupric oxide with a halide source, usually a hydrogen halide such as HCl or HBr, with one or more amines in the presence of an organic solvent. Suitable amines include tertiary or secondary alkaline diamines, secondary monoamines, primary monoamines, tertiary monoamines and mixtures thereof. Suitable amine mixtures are disclosed in U.S. Pat. Nos. 3,306,874; 3,306,875; 3,941,266; 3,988,287; 4,028,341 and 4,054,553.
In copending application Ser. No. 572,036 new copper(I)-diamine-phenoxide complexes which are useful for polyphenylene oxide preparation are disclosed. These complexes, represented by the formula below, are a single catalyst species which can be prepared in substantially pure, crystalline form. ##STR2## The radical R.sup.1 is hydrogen or alkyl, R.sup.2 is an alkyl radical, with the provisos that (1) R.sup.1 and R.sup.2 taken together contain 4 to 6 carbon atoms and (2) when R.sup.1 is hydrogen, R.sup.2 is tertiary alkyl, and each of R.sup.3 and R.sup.4 is independently selected from hydrogen or methyl radicals.
Complexes of this structure are prepared by first reacting cuprous chloride with a diamine of the formula: ##STR3## to form a copper(I)-diamine-chloride complex.
The copper(I)-diamine-phenoxide complexes are obtained by reacting an alkali metal salt of a hydroxy aromatic compound of the formula below with the copper(I)-diamine-chloride complex described above. ##STR4## This reaction requires scrupulous exclusion of moisture and air, since the complexes are very sensitive to both. The preparation operations are normally conducted under a nitrogen atmosphere. The alkali metal chloride by product precipitates from the solution and is removed by filtration or the like, whereupon the substantially pure crystalline complex of this invention may be isolated by removal of the organic liquid.
Although the above method provides a suitable copper(I)-diamine-phenoxide complex for polyphenylene oxide polymerization, manipulation of this complex is difficult due to its extreme air and moisture sensitivity. It is desirable to obtain a simplified process which provides the catalysis of copper(I)-diamine phenoxide complexes in the preparation of polyphenylene oxide without complicated operating steps.